There is known an insulated bus pipe (busbar section) including: an insulated pipe, a grounding layer, a partly conductive layer, end cheeks (flanges) secured to a casing, and bar contacts having holes (Arrangements of cast insulation busbars, RAUTA-ENERGO).
A number of patent documents disclose a busbar section including a conductive bar having a circular cross-section, a first insulation shell embracing the bar, a second insulation shell, wherein the thickness of the second insulation shell is greater that the thickness of the first insulation shell, a protective layer over the second insulation shell, and a section insulation jacket covering the protective layer (U.S. Pat. No. 4,767,894), as well as busbar sections each including a bar disposed inside insulation layers (WO2010090034A1; CN201527833U).
A prior art busbar section closest to the busbar section claimed herein is a busbar section described in RU2439764C1, including three embodiments.
The first embodiment of the busbar section of RU2439764C1 includes a conductive bar made of an aluminum tube, or a copper tube, or a rod; the bar having end contacts integral with flanges having threaded holes receiving nipples. A graphite layer is disposed on the outer surface of the bar, conduction layers made of conductive paper interlaced with insulation layers made of insulation paper are wrapped over the graphite layer. An aluminum layer made of aluminum foil is disposed over the outer conduction layer and copper strips made of copper foil are positioned over the aluminum layer at the opposite sides of the bar. A layer of insulation paper is wrapped over the copper strips. A flexible heat-shrink tube is placed over the layer of insulation paper in the middle part of the busbar section. A terminal flexible heat-shrink tube is placed at each end part of the busbar section, wherein the terminal heat-shrink tube overlaps the middle heat-shrink tube. All the above-indicated layers of paper, gaps between the layers and gaps between the heat-shrink tubes are filled with a cured epoxy resin and connections of the heat-shrink tubes are made hermetical. A protective steel pipe is disposed over the heat-shrink tubes. All the above-indicated layers of the busbar section are located along the bar length between the flanges of the bar contacts. A grounding contact is provided in the busbar section, the contact connected to the copper strips, wherein the grounding contact is located at the outer surface of the protective steel pipe.
The second embodiment of the busbar section of RU2439764C1 includes a conductive bar made of an aluminum tube, or a copper tube, or a rod, the bar having end contacts integral with flanges having threaded holes receiving nipples. A graphite layer is disposed on the outer surface of the bar, conduction layers made of conductive paper or fabric interlaced with insulation layers made of insulation paper or fabric are wrapped over the graphite layer. An aluminum layer made of aluminum foil is disposed over the outer conduction layer, a copper layer made of copper foil is disposed over the aluminum layer and copper strips made of copper foil are positioned at the opposite sides of the bar. A layer of insulation paper is wrapped over the copper layer. A heat-shrink tube is placed over the layer of insulation paper in the middle part of the busbar section. A flexible terminal heat-shrink tube is placed on each end part of the busbar section, wherein the terminal heat-shrink tube overlaps the middle heat-shrink tube. All the above-indicated layers of paper, gaps between the layers and gaps between the heat-shrink tubes are filled with a cured epoxy resin and connections of the heat-shrink tubes are made hermetical. All the above-indicated layers of the busbar section are located along the bar length between the flanges of the bar contacts.
The third embodiment of the busbar section of RU2439764C1 includes a conductive bar made of an aluminum tube, or a copper tube, the bar having an inside chamber and end contacts integral with flanges having threaded holes receiving nipples. Insulation layers and conduction layers are disposed on the outer surface of the bar and the conduction layers are electrically connected to a grounding contact of the busbar section. A flexible heat-shrink tube is placed over the outer layer in the middle part of the busbar section. A terminal flexible heat-shrink tube is placed on each end part of the busbar section, wherein the terminal heat-shrink tube overlaps the middle heat-shrink tube. All gaps between the heat-shrink tubes and the layers of the busbar section are filled with a cured epoxy resin and connections of the heat-shrink tubes are made hermetical. All the above-indicated layers of the busbar section are located along the bar length between the flanges, wherein at least one hole communicated to the chamber of the bar is provided in each of the flanges.
The first embodiment of the known busbar section of RU2439764C1 shall be used in external busbar systems to be mounted outside buildings. The bar of the busbar section has contacts welded to the butt ends of the bar and the flanges are integral with the contacts. All pinholes of the layers and gaps between the layers of the busbar section and the heat-shrink tubes are filled with an epoxy resin. Two layers of a heat-shrink polyether jacketing tape is wound over the heat-shrink tube in overlapping manner. A protective steel tube case is placed over the jacketing tape.
The second embodiment of the known busbar section of RU2439764C1 shall be used in internal busbar systems to be mounted inside buildings. This busbar section includes all the above-indicated features of the first embodiment except for the protective steel tube case.
Both the embodiments of the busbar section, according to RU2439764C1, provide for a supporting tube layer made of a crepe kraft paper having a density of 100 to 120 g/m2, wherein the thickness of the paper layer is 0.15 to 0.5 mm. In the operational condition, this paper is impregnated with a plasticized epoxy resin. Viscosity of the resin is predetermined and it allows the resin to be cured at 140° C., while maintaining a constant viscosity in the temperature range of 20° C. to 80° C. Both the embodiments of the busbar section include sealing the connection areas of the heat-shrink tubes with a self-adhesive tape made of polyisobutylene.
Additionally, it is provided that the heat-shrink properties of the terminal heat-shrink tube are better than the same of the middle heat-shrink tube.
The third embodiment of the known busbar section provides for cooling the busbar.
The bar of RU2439764C1 is insulated as follows. A composition (e.g. a graphite composition) allowing insulation resin to be detached from the bar is placed on the bar surface between the bar contacts. Nipples are inserted into the threaded holes of the contacts, then layers of a partly conductive paper or a partly conductive fabric interlaced with an isolation paper are wrapped over the bar, wherein a partly conductive layer is formed on the outer layer of the partly conductive paper, the partly conductive layer being a grounding layer. Then aluminum foil is wrapped over the busbar section, thus forming a grid on the partly conductive layer. A copper foil is soldered to the aluminum foil at the both sides of the busbar, and the copper foil is connected to a grounding contact used for connecting the busbar section to a ground loop. The grounding contact is filled with a heat-resistant fatty lubricant and then the grounding contact is sealed. The above-indicated graphite is used in the busbar section in order to allow the insulation resin to be detached from the bar.
Some embodiments of the busbar section of RU2439764C1 include cooling chambers which may be used for delivering cooling air, cold-proof coolant or water from a cooling system. Circulation of the cooling medium through a closed path improves the heat drain from the busbar sections, compensation members and contacts. When the busbar is meant to work at a higher operational temperature, then the third embodiment of the busbar section is used in order to avoid its damage due to overheating. The way of working of the third embodiment is the same as of the first and the second embodiments.
The busbar sections of RU2439764C1 have improved reliability owing to the efficient way of grounding the sections, so as the insulation body of each busbar section and each joint sleeve is grounded separately, and disruption due to potential difference between the bar and the insulation is avoided. Additionally, reliability is improved owing to cooling the busbar section in order to assure effective protection of the busbar against overheating. Cooling the busbar allows maintaining the throughput capability thereof.
The common features of the known busbar section embodiments of RU2439764C1 and the two embodiments of the claimed busbar section are as follows. Each busbar section contains a conductive bar (pipe) having end contacts and disposed within electrical insulation, a grounding shield covering the bar insulation, and a metal case having an outer fire-resistant coating (RU2439764C1, Jan. 10, 2012, the closest prior art).